A nanosecond pulse power supply for micro-ECM (Electrochemical Machining) has been developed, and the minimum pulse on-time is 50 ns. After the influence of ultra-short pulse on micro-ECM was analyzed, complementary chopper circuit was presented to avoid waveform distortion, which can achieve higher pulse frequency. A fast protect circuit was designed, and its response time is less than 5μs, which can avoid damaging workpiece and electrical components by switching off machining voltage and step motor as soon as a short circuit was detected. A series of ECM experiments using the power supply have been carried out, and results of test have proved that high frequency, short pulse width power supply helps to achieve better quality surface, higher machining accuracy.